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THE ROYAL SOCIETY OF CANADA 



phere it gradually attains the temperature of its boiling point at 

 atmospheric pressure. Heat always leaks into the liquid so that 

 the liquid is always boiling away. Therefore we measured first of all 

 the wastage of oxygen before the electrical circuit was completed. 

 This gave us on an average about 120cc. per half minute. The 

 current was applied for a half minute and while one observer manipu- 

 lated the apparatus, the other read the ammeter and voltmeter, and 

 at the end of the half minute read the gas liberated. If the gas liberated 

 per half minute is 750 cc, then, allowing for the leakage, the heat 

 supplied by the current has been responsible for the evaporation of 

 630 cc. of oxygen. If, for example, the current was 2 • 56 amperes and 

 the voltage 2-46 volts, the heat supplied =2-56X2-46X30X -24 

 calories. The density of oxygen gas at the time of the experiment 

 being -00130 gm. per cc. the mass of oxygen evaporated = -00130X630 

 gm. and therefore the latent heat of evaporation 



= 2-56X2-46X30X-24 

 630 X -00130 



= 55 calories per gm. 

 The following table gives the readings obtained with oxygen: 



Whence L = 



6-3X-24X30 



= 55 calories per gm. 



630X -00130 



The number quoted in the Smithsonian tables is 51 calories 

 per gm. 



The experiment was repeated with liquid methane at a temper- 

 ature of —160° on our pentane thermometer. The wastage per 

 minute was first determined. It was about 160 cc. The graduated 



